The meaning of Ramadan and Sawm (Fast)

Ramadan is taken from the word ra-ma-da which means ‘to burn’ or ‘that which is intensely or vehemently heated by the sun’. And the word Ramdhā means ‘the intense heat of the sun’. [The Arabs used to say about] the sheep that they were ‘burned (ramidat) while they were grazing under the scorching heat of the sun to the extent that their livers became damaged (by the intense heat of the sun). Ramadan was named such because it burns the sins of the believers.
[Mufradāt al-Qur’ān]

Imam al-Qurtubi said:

This month was named Ramadan because it burns the sins of people with righteous deeds.
[Tafsīr al-Qurtubī]

On the meaning of Sawm, Ahmad Mayyara said:

Linguistically, the root meaning of the word sawm (fast) is ‘to refrain or abstain from’…. Legally (in terms of Shari’ah), sawm (fast) refers to ‘refraining from two appetites of the stomach and the private parts for a whole day (from the first light of dawn to sunset) with the (following) intentions:

to come closer to Allah; that is to fast for His sake alone, and

to fulfil the legal obligation; in order to
—a) oppose the desires which are responsible for the two appetites,
—b) bring the nafs – the self – under control,
—c) polish the mirror of the intellect,
—d) take on angelic attributes,
—e) arouse the slave’s concern for those who are hungry.